Normal, dysplastic, and malignant mammary tissues are each composed of heterogeneous populations of cells. The objectives of the proposed research are to delineate specific cellular markers for distinguishing the different types of epithelial cells in these tissues and to identify and characterize cell surface factors which might be involved in mediating the interactions of these cells with each other and with extracellular substrata to which they attach. The workscope of this proposal includes three basic approaches utilizing in vitro methodology. First, lectins in conjunction with other agents will be used to attempt to define common and unique surface-related features of the different types of mammary cells. Second, factors involved in homotypic and heterotypic intercellular adhesion and in cell-substratum adhesion will be investigated to determine if the normal, dysplastic, and malignant cells differ in these functions. Third, extra-cellular material apparently produced by the cells will be studied to establish if the material is part of an extracellular matrix formed by the cells and if there are qualitative or quantitative differences in its production by the different cell types. Results of these endeavors hopefully will lead to a more comprehensive understanding of the roles and fate of each epithelial cell type during the pathogenesis of mammary neoplasia.